You question is very broad, but assuming you are asking about application of the cooling off period to the membership with JA as it is a service offered online and not "on-premises or face to face" then you ought to be guided by The Consumer Contracts (Information, Cancellation and Additional Charges) Regulations 2013
Section 30 which is essentially the cooling off period provides:
30.—(1) The cancellation period ends as follows, unless regulation 31 applies.
(2) If the contract is—
(a)a service contract, or
(b)a contract for the supply of digital content which is not supplied on a tangible medium,
the cancellation period ends at the end of 14 days after the day on which the contract is entered into
Your right to cancel is provided under clause 29 and the same clause gives you the exceptions and relevant to your question is section 29(1)(d) which states:
29.—(1) The consumer may cancel a distance or off-premises contract at any time in the cancellation period without giving any reason, and without incurring any liability except under these provisions—;
(d)regulation 36(4) (where consumer requests early supply of service).
Finally under section 36 you lose the right to cancel if the service has been provided and with your acknowledgement.
So yes all distance, off-premises contracts have the 14 days cooling off period however depending on the actions of both consumer and trader during that 14 day period that right to cancel is qualified.
I hope this helps and I would be grateful for your rating at your earliest convenience. all the best